Paving material and method of preparing same



Patented Oct. 28,- #1930 UmrEo; S ATES? PATENror-F ms I aivnsm A. YOUNG} ANDVGLENVN H. ALVEY, or IsAiv N'roNIo, Texas, AssIG roRs'ro UVALDE ASPHALT COMPANY, OF BEAUMONT, TEXAS, A CORPORATION OF TEXAS No Drawing.

County, Texas, although other generally Sim ilar materials may befused; This Uvalde rock asphalt consists of a comparatively porous I shell limestone impregnated naturally with asphalt which thoroughly fills the pores in the rock. 7

Thegeneral methodof using this material for paving purposes has beento crush and grade it and then to heat it and treat it with a flux such as asnhalticoilor a ara-fline base oil.- It is then neces'saryto lay and compact the material withoutgreat delay as it tends to cake and set as it cools.- t

Since the heating and treatment with the flux oil must take place nearthe work, it is necessary to setup paving mixing plants at Y various points and the 'expense ofiiistalla tion'and maintenance of these plants adds materially'to the cost of the paving.

A cold mixing process has also been developed in'whichthe crushed rock asphalt is mixed cold with a flux, usually an asphaltic base oil. A solvent such as kerosene is also generally added to den the setting of the I mix; This mix tends toset as the volatiles in the flux and solvent evaporate and can not be transported successfullly for verygreat distances from a paving'plant. VWhen transported the mix cakes in the. cars and must 40 be broken up withpick axes or. similar tools to remove it from thecarsa Thisv adds very greatly to the expense and this method is therefore not commercially practicalfo-r producing a mix "to beused at considerable dis- 1 tances from a paving plant.-

Application filed June 20,

' sav ng, MAIEBIAL AND METHOD or: PREPARING SAME 1927. Serial no. 290,306.

It is an objectof the present invention to i provide a new and improved method of pre paring a paving material or the like, and such a material which may be mixed and handled cold and may be transported before placing Without serious caking of the J material.

It is a further object ofthe'invention to provide a method and mixtureby whichthe natural set of the basic mixture -1s retarded b the addition of other elements and in which the retardation of the set may be cone 3 trolled by the amount and relation of elements ofthemixture;

It is an'additiohal objectto'provide a pavingmaterial of this type having incorporated thereinan' excess of certain sizes of relatively harder material whereby the softer material is crushed and forcedinto intimate contact It is also an object, to produce a paving material which willgive a surface of a character adapted to minimize or .preventthe skidding of vehicles on" the surface.

Other and further objects will appear as the description proceeds.

The basic'element in our improved paving material-is the natural rock asphalt such as Uval'de asphalt which we 'have'referred to specifically above, Thisconsists of a rela-- tively soft porous shell limestone impregmated with asphalt or bitumen. This asphalt the f forms from about eight totivelve per cent of the commercially used material. The as phaltic-rock s crushed and graded according to sizes and a m xture s formedwhich is so proportioned as to give a minimum of voids. This mixture is what 1s known; asa balanced mix and affords a compact pavement "or the likc substantially impervious to water and without air pockets. l This rockasphalt is treated with a flux which tends. to soften the asphalt in the rock and cause the particles of the material to adhere to each other. If the material were used without any further addition it would cake and pack in transportation soas to make it impractical to carry it any great distance from the mixing plant for use. In order toretard the set of the material we add to the mixture a small quantity of a solvent which may be kerosene or any other light petroleum distillate. This fluid has a solvent action both on the asphalt of the rock and AIfurther element which we incorporate in,

our paving material consists in a crushed rock which 18 harder than the limestone rock asphalt. This crushed rock may be a rock such as trap rock or hard limestone and is preferably screened so as to eliminate the smaller particles. We have found that the most satisfactory results will be obtained by using a one-size crushed trap rock substantially the same size as the larger portions of the rock asphalt aggregate. In laying pavements of ordinary thickness, this size would be from one-fourth to one-half inch. The crushed hard rock when added to the crushed rock asphalt serves tounbalance the total mixture; that is, it will give tothe total mixture a preponderance of larger aggregate so that the smaller aggregate and fine particles present will not be sufficient to fill up all voids in the mixture. This fact tends to retard the set of the material as it will'cause the particles to be largely separated by air spaces. When the material is laid and compacted, however, the hard rock will be forced intothe particles of rock asphalt and these particles will be further crushed so that a solid and compact pavement will result. The hard rock which extends throughout the paving gives a surface which is efficient in preventing skidding.

We have found that a very material differonce may be made inthe rate of set of the material, not only by varying the quantities of the several elements but also by varying the order in which the elements are mixed together. For example, the crushed rock asphalt may first have added thereto the flux and solvent mixed together. In this case the solvent is merely thinned by the flux and its action therefore retarded since it is renderedless sticky. The action will be fur ther retardedif the solvent is first addedto the rock asphalt which is thus thoroughly wetted with the solvent before the flux is applied. A still further retardation in set may be accomplished by initially dampening the rock asphalt with water before applying the solvent and flux. The wet rock asphalt will not be permeated by the flux and solvent until the water has largely evaporated as the oil will not mix with the water.

Another manner in which the materials may be mixed is by applying the flux and solvent to the crushed rock asphalt. then wetting the crushed hard rock with water and mixing the damp rock with the treated rock asphalt. The dampness of the rock prcvents it from being immediately coated with the solvent and flux and serves to separate the particles of rock asphalt and to retard the set. If desired, the rock asphalt and hard rock may be mixed together and the solvent, flux and water may be added in the form of an emulsion. In some cases where long delay of set is desired, it; may be found advisable towet both the rock asphaltand rock before applying the flux and solvent, and mixing the mass together.

It will be apparent therefore that our materials, may be mixed together in .a variety of ways and that the method and order of mixture may be adapted to the particular needs of the temperatures present and the length of time and the distance required for transportation. These elements will preferably beso adjusted that when the material is spread out in a thin layer on the surface being covered, the volatile solvent and any water present will be sufficiently evaporatedv in a short time, such as a half hour, so that the material may be compacted by a heavy steam roller or the like and formed into a dense water-proof surface.

While the several elements of our mixture may be widely varied in proportion. the mixture will generally consist of from ten to thirty-three per cent of hard rock, from sixty to ninety per cent rock asphalt, and from one to three per cent flux; and, where solvent or water or both are used, from one to three per cent solvent and from one-half to two per cent or more of water.

While our material is particularly adapted for paving purposes in paving streets and roadways, it will be understood that it is also capable of many other uses. For example, it may be used to pave sidewalks or floors in buildings and may also be used in covering roofs. In view of its impermeability, it has also proved of valuev in covering the bottoms of reservoirs or chambers for holding liquid. The material is also efiicient in dampening vibrations and is therefore particularly useful in bridge coverings, industrial flooring, railroad platforms and crossings, and engine foundations.

While we have given by way of example, certain preferred methods of mixing and preferred proportions, our invention is capable ofwide modification and we contemplate such changes and modifications as come within the spirit and scope of the appended claims. I

We claim:

1. The method of making a paving composition or the like which comprises crushing rock asphalt, making up a mass crushed rock asphalt sized and proportioned to give a balanced mixture having a mini mum of voids, treating said rock asphalt with a flux, and adding to said mixture a crushed rock which is harder than the rock asphalt and which is in sizes and quantity such as to create void-s in the total mixture.

2. The method of making a paving composition or the like which comprises crushing rock asphalt. making up a mass of said crushed rock asphalt sized and proportioned togive a balanced mixture having a mini- 1 mum of voids treatin said rock as halt with a flux, and addingto said mixture a dampened crushed rock which is harder than the crushed rock asphalt and which is in size and quantity total mixture.

3. The method of making a paving composition or the like whichcomprises crushing ing rock asphalt, making up a mass of said crushed rock asphalt sized and proportioned to give a balanced mixture having a minimum of voids, treating said rock asphalt with a solvent andwith a flux, and adding to said mixture a crushed rock which is harder than the crushed rock asphalt and which is substantially the size ofthe coarser of said rock asphalt, said asphaltbeing sized and proportioned to a balanced mixture with a minimum of voids, a flux, and crushed rock I it harder than the crushed rock asphalt, said rock being so sized and in such quantity as to produce voids in :the entire mixture.

' Signed at San Antonio,

of June, 1927.

ERNEST A. 'YOUNG. GLENN H. ALVEY.

Texas, this 16 dayf such as to create voids in the rock asphalt aggregate, said rock being i added in such quantity as to create voids in the total mixture.

5. The method of making a paving composition or the like which comprises crushing rock asphalt, making up a mass of said asphalt sized and proportioned to give a bal aneed. mixture having a-minimum of voids,

' dampening said asphalt with Water, treat ing said asphalt with a solvent and with a flux, and mixing withthe asphalt a crushed rock harder than the rock asphalt, said rock being in such sizes and quantity as to create voids in the entire mixture.

6. A paving mixture comprising damp v crushed rock asphalt, said asphalt being sized and proportioned to a balanced mixture with a minimum ofvoids, a flux, and

damp crushed rock harder than the crushed rock asphalt, said rock being in size and quantity such as to create voids in the entire mixture.

7. A pavingmixture comprising crushed 

